Why comparing characters with .Equals always returns false?
char letter = 'a';
Console.WriteLine(letter.Equals("a")); // false
Overall I'm trying to write an English - Morse Code translator. I run into a problem comparing char values which shown above. I began with a foreach to analyze all the characters from a ReadLine() input, by using the WriteLine() method, all the characters were transposed fine, but when trying to compare them using the .Equals() method, no matter what I did, it always output false when trying to compare chars.
I have used the .Equals() method with other strings successfully, but it seems to not work with my chars.
using System;
public class MorseCode {
public static void Main (string[] args) {
Console.WriteLine ("Hello, write anything to convert it to morse code!");
var input = Console.ReadLine();
foreach (char letter in input) {
if(letter.Equals("a")) {
Console.WriteLine("Its A - live");
}
Console.WriteLine(letter);
}
var morseTranslation = "";
foreach (char letter in input) {
if(letter.Equals("a")) {
morseTranslation += ". _ - ";
}
if(letter.Equals("b")) {
morseTranslation += "_ . . . - ";
}
if(letter.Equals("c")) {
morseTranslation += "_ . _ . - ";
}
...
}
}
Console.WriteLine("In morse code, " + input + " is '"morseTranslation + "'");
}
}
At the beginning, I wrote the foreach to test if it recognized and ran the correct output, but in the end, when I wrote "sample" into the ReadLine(), it gave me :
Hello, write anything to convert it to morse code!
sample
s
a
m
p
l
e
When you do this:
var c = 'x';
var isEqual = c.Equals("x");
the result (isEqual) will always be false because it's comparing a string to a char. This would return true:
var isEqual = c.Equals('x');
The difference is that "x" is a string literal and 'x' is a char literal.
Part of what makes this confusing is that when you use an object's Equals method, it allows you to compare any type to any other type. So you could do this:
var x = 0;
var y = "y";
var isEqual = x.Equals(y);
...and the compiler will allow it, even though the comparison between int and string won't work. It will give you this warning:
When comparing value types like int or char with other values of the same type, we usually use ==, like
if (someChar == someOtherChar)
Then if you tried to do this:
if(someChar == "a")
It wouldn't compile. It would tell you that you're comparing a char to a string, and then it's easier because instead of running the program and looking for the error it just won't compile at all and it will tell you exactly where the problem is.
Just for the fun of it, here's another implementation.
public static class MorseCodeConverter
{
private static readonly Dictionary<char, string> Codes
= CreateMorseCodeDictionary();
public static string Convert(string input)
{
var lowerCase = input.ToLower();
var result = new StringBuilder();
foreach (var character in input)
{
if (Codes.ContainsKey(character))
result.Append(Codes[character]);
}
return result.ToString();
}
static Dictionary<char, string> CreateMorseCodeDictionary()
{
var result = new Dictionary<char, string>();
result.Add('a', ". _ - ");
result.Add('b', "_ . . . - ");
// add all the rest
return result;
}
}
One difference is that it's a class by itself without the console app. Then you can use it in a console app. Read the input from the keyboard and then call
MorseCodeConverter.Convert(input);
to get the result, and then you can print it to the console.a
Putting all of the characters in a dictionary means that instead of repeating the if/then you can just check to see if each character is in the dictionary.
It's important to remember that whilst the char and string keywords look reminiscant of eachother when looking at printed values you should note that they are not accomodated for in exactly the same way.
When you check a string you can use:
string s = "A";
if(s.Equals("A"))
{
//Do Something
}
However, the above will not work with a char. The difference between chars (value types) and strings (reference types) on a surface level is the use of access - single quote (apostrophe) vs quote.
To compare a char you can do this:
char s = 'A';
if(s.Equals('A'))
{
//Do Something
}
On a point relevant to your specific case however, morse code will only requre you to use a single case alphabet and as such when you try to compare against 'A' and 'a' you can call input.ToLower() to reduce your var (string) to all lower case so you don't need to cater for both upper and lower case alphabets.
It's good that you're aware of string comparissons and are not using direct value comparisson as this:
if (letter == 'a')
{
Console.WriteLine("Its A - live");
}
Would've allowed you to compare the char but it's bad practice as it may lead to lazy comparisson of strings in the same way and this:
if (letter == "a")
{
Console.WriteLine("Its A - live");
}
Is a non-representitive method of comparison for the purpose of comparing strings as it evaluates the reference not the direct value, see here
For char comparison you have to use single quote ' character not " this.
By the way it writes sample in decending order beacuse in your first foreach loop you write all letters in new line. SO below code will work for you:
using System;
public class MorseCode {
public static void Main (string[] args) {
Console.WriteLine ("Hello, write anything to convert it to morse code!");
var input = Console.ReadLine();
/*foreach (char letter in input) {
if(letter.Equals("a")) {
Console.WriteLine("Its A - live");
}
Console.WriteLine(letter);
}*/
var morseTranslation = "";
foreach (char letter in input) {
if(letter.Equals('a')) {
morseTranslation += ". _ - ";
}
if(letter.Equals('b')) {
morseTranslation += "_ . . . - ";
}
if(letter.Equals('c')) {
morseTranslation += "_ . _ . - ";
}
...
}
}
Console.WriteLine("In morse code, " + input + " is '"morseTranslation + "'");
}
}
In C#, you can compare strings like integers, that is with == operator. Equals is a method inherited from the object class, and normally implementations would make some type checks. char letter is (obviously) a character, while "a" is a single lettered string.
That's why it returns false.
You could use if (letter.Equals('a')) { ... }, or simpler if (letter == 'a') { ... }
Even simpler than that would be switch (letter) { case 'a': ...; break; ... }.
Or something that is more elegant but maybe too advanced yet for a beginner, using LINQ:
var validCharacters = "ABCDE...";
var codes = new string[] {
".-", "-...", "-.-.", "-..", ".", ...
};
var codes = input.ToUpper() // make uppercase
.ToCharArray() // explode string into single characters
.Select(validCharaters.IndexOf) // foreach element (i. e. character), get the result of "validCharacters.IndexOf",
// which equals the index of the morse code in the array "codes"
.Where(i => i > -1) // only take the indexes of characters that were found in "validCharacters"
.Select(i => codes[i]); // retrieve the matching entry from "codes" by index
// "codes" is now an IEnumerable<string>, a structure saying
// "I am a list of strings over which you can iterate,
// and I know how to generate the elements as you request them."
// Now concatenate all single codes to one long result string
var result = string.Join(" ", codes);
Related
I am creating a console application upon which the user can type in a train station and find the train stations. For this, I am appending the Console.ReadKey().Key to a String each time.
When the user types an incorrect letter, I want the ConsoleKey.Backspace to remove the last Char in the String.
private void SetDepartingFrom()
{
String searchQuery = "";
ConsoleKey keyIn;
while ((keyIn = readKey(searchQuery)) != ConsoleKey.Enter)
{
if (keyIn == ConsoleKey.Backspace)
{
searchQuery.TrimEnd(searchQuery[searchQuery.Length - 1]);
}
else
{
searchQuery += keyIn.ToString();
}
}
}
private ConsoleKey readKey(String searchQuery)
{
Console.Clear();
Console.WriteLine("Stations Found:");
if (searchQuery != "")
App.Stations.FindAll(x => x.GetName().ToUpper().Contains(searchQuery.ToUpper())).ForEach(x => Console.WriteLine(x.GetName()));
else
Console.WriteLine("No Stations found...");
Console.Write("Search: " + searchQuery);
return Console.ReadKey().Key;
}
I have tried the following:
if (keyIn == ConsoleKey.Backspace)
searchQuery.TrimEnd(searchQuery[searchQuery.Length - 1]);
if (keyIn == ConsoleKey.Backspace)
searchQuery.Remove(searchQuery.Length -1);
if (keyIn == ConsoleKey.Backspace)
searchQuery[searchQuery.Length -1] = "";
None have worked. I understand Strings are immutable in C#, however, is this possible or is there a better way to achieve this?
Thanks in advance.
String is immutable so you have to use the value returned by TrimEnd.
searchQuery = searchQuery.TrimEnd(searchQuery[searchQuery.Length - 1]);
In this case I think Substring method would be more appropriate.
As you noted, strings are immutable. All of the instance methods on the string type (at least those related to "modifying" it) return a new string. This means that calling something like the following returns a new string which is immediately discarded:
// value is discarded
searchQuery.Substring(0, searchQuery.Length - 1);
The solution is to reassign the variable with the new value. For example:
searchQuery = searchQuery.Substring(0, searchQuery.Length - 1);
SharpLab example
If you are using C# 8 you can make use of the range operator via the Index/Range classes. This provides a bit cleaner version:
// backspace one character
searchQuery = searchQuery[..^1];
SharpLab example
I will also note that TrimEnd is most likely not what you want. It will trim more than one character at a time which isn't what a single press of the Backspace key would do. For example consider the following:
var str = "Abcdeee";
var result = str.TrimEnd('e');
Console.WriteLine(result); // prints "Abcd"
SharpLab example
Any method you use to manipulate the string will return the new string so you need to capture that.
string newString = searchQuery.Substring(0, searchQuery.Length -1);
It will return a new string, so you need to assign it to a string like this.
string newStr = earchQuery.Remove(searchQuery.Length -1);
Or to same string you can do like this.
earchQuery= earchQuery.Remove(searchQuery.Length -1);
You can also use TrimEnd and SubString methods.
You may try the following code example which removes the last character from a string.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
namespace Rextester
{
public class Program
{
public static void Main(string[] args)
{
string founder = "Hell World from Big_Data_Analyst!";
string founderMinus1 = founder.Remove(founder.Length - 1, 1);
Console.WriteLine(founderMinus1);
}
}
}
The input string in the code is
Hell World from Big_Data_Analyst!
The output string is
Hell World from Big_Data_Analyst
As you see the last character which is ! is being removed in the output
I am designing an API where the API user needs Arabic text to be returned in Unicode format, to do so I tried the following:
public static class StringExtensions
{
public static string ToUnicodeString(this string str)
{
StringBuilder sb = new StringBuilder();
foreach (var c in str)
{
sb.Append("\\u" + ((int)c).ToString("X4"));
}
return sb.ToString();
}
}
The issue with the above code that it returns the unicode of letters regardless of its position in word.
Example: let us assume we have the following word:
"سمير" which consists of:
'س' which is written like 'سـ' because it is the first letter in word.
'م' which is written like 'ـمـ' because it is in the middle of word.
'ي' which is written like 'ـيـ' because it is in the middle of word.
'ر' which is written like 'ـر' because it is last letter of word.
The above code returns unicode of { 'س', 'م' , 'ي' , 'ر'} which is:
\u0633\u0645\u064A\u0631
instead of { 'سـ' , 'ـمـ' , 'ـيـ' , 'ـر'} which is
\uFEB3\uFEE4\uFEF4\uFEAE
Any ideas on how to update code to get correct Unicode?
Helpful link
The string is just a sequence of Unicode code points; it does not know the rules of Arabic. You're getting out exactly the data you put in; if you want different data out, then put different data in!
Try this:
Console.WriteLine("\u0633\u0645\u064A\u0631");
Console.WriteLine("\u0633\u0645\u064A\u0631".ToUnicodeString());
Console.WriteLine("\uFEB3\uFEE4\uFEF4\uFEAE");
Console.WriteLine("\uFEB3\uFEE4\uFEF4\uFEAE".ToUnicodeString());
As expected the output is
سمير
\u0633\u0645\u064A\u0631
ﺳﻤﻴﺮ
\uFEB3\uFEE4\uFEF4\uFEAE
Those two sequences of Unicode code points render the same in the browser, but they're different sequences. If you want to write out the second sequence, then don't pass in the first sequence.
Based on Eric's answer I knew how to solve my problem, I have created a solution on Github.
You will find a simple tool to run on Windows, and if you want to use the code in your projects then just copy paste UnicodesTable.cs and Unshaper.cs.
Basically you need a table of Unicodes for each Arabic letter then you can use something like the following extension method.
public static string GetUnShapedUnicode(this string original)
{
original = Regex.Unescape(original.Trim());
var words = original.Split(' ');
StringBuilder builder = new StringBuilder();
var unicodesTable = UnicodesTable.GetArabicGliphes();
foreach (var word in words)
{
string previous = null;
for (int i = 0; i < word.Length; i++)
{
string shapedUnicode = #"\u" + ((int)word[i]).ToString("X4");
if (!unicodesTable.ContainsKey(shapedUnicode))
{
builder.Append(shapedUnicode);
previous = null;
continue;
}
else
{
if (i == 0 || previous == null)
{
builder.Append(unicodesTable[shapedUnicode][1]);
}
else
{
if (i == word.Length - 1)
{
if (!string.IsNullOrEmpty(previous) && unicodesTable[previous][4] == "2")
{
builder.Append(unicodesTable[shapedUnicode][0]);
}
else
builder.Append(unicodesTable[shapedUnicode][3]);
}
else
{
bool previouChar = unicodesTable[previous][4] == "2";
if (previouChar)
builder.Append(unicodesTable[shapedUnicode][1]);
else
builder.Append(unicodesTable[shapedUnicode][2]);
}
}
}
previous = shapedUnicode;
}
if (words.ToList().IndexOf(word) != words.Length - 1)
builder.Append(#"\u" + ((int)' ').ToString("X4"));
}
return builder.ToString();
}
I have a string aaaaabbbbbccccc I have a dictionary that has certain rules
Dictionary<string, string> rules = new Dictionary<string, string>();
rules.Add("abc", "aab");
rules.Add("ac", "ba");
rules.Add("cb", "cc");
This means if string has abc it will be replaced with aab but string doesn't have any rules that match. So, I am creating a new string out of the old string based on these rules. For instance, if I rearrange the old string to abcabcabcabcabc then rule can be applied. But I am stuck at rearranging. I tried using IndexOf and Remove functions but I didn't get the positive output. This is my code
string s;
s = "aaaaabbbbbccccc";
string newString = "";
int ia, ib, ic;
//Formulating rule 1
if (s.Contains("a") && s.Contains("b") && s.Contains("c"))
{
ia = s.IndexOf("a");
ib = s.IndexOf("b");
ic = s.IndexOf("c");
if (ia < ib && ib < ic)
{
newString += "abc";
s.Remove(ia, 1);
s.Remove(ib, 1);
s.Remove(ic, 1);
}
}
Console.WriteLine("New String " + newString);
Console.WriteLine("Old String " + s);
I am getting
New String abc
Old String aaaaabbbbbccccc //Which is wrong.
Can anyone help what I am doing wrong or is there any better way?
Your explanation does not match your code.
In your explanation, you say that aaaaabbbbbccccc does not match any rule (e.g. the "abc" rule). However, in your code, you are not checking if it contains "abc", but rather that it contain "a" and "b" and "c", not necessarily as a single chunk:
if (s.Contains("a") && s.Contains("b") && s.Contains("c"))
This is an important difference:
aaaaabbbbbccccc does not contain abc (rule does not apply)
aaaaabbbbbccccc does contain a, b and c (rule does apply)
You're contradicting yourself. Which is correct here, the code or your explanation? Does the rule check for the exact string, or does it check for all characters separately?
Awkward string manipulation.
Based on your code; I infer that you're not experienced with some very common string operations (no offense intended). Unless you contradict me, I'm going to assume that your explanation is correct and your code is not.
Checking if a string contains a substring:
As I explained previously, there is an important difference between checking is a string contains a substring:
s.Contains("abc") //1
and checking if a string contains each individual character of a substring:
s.Contains("a") && s.Contains("b") && s.Contains("c") //2
As a more practical example; does my username (Flater) contain the substring "Fertla"?
If you use the logic in //1, the answer is no.
If you use the logic in //2, the answer is yes.
Based on your explanation, you should be using //1
Replacing a string:
This means if string has abc it will be replaced with aab
There is a very simple method for this:
s.Replace("abc", "aab");
Some examples:
abcdef becomes aabdef
abcabcabc becomes aabaabaab (it replaces all occurrences)
uvwxyz becomes uvwxyz (if it doesn't occur, nothing gets replaced)
Take note of the second and third bullet point.
String.Replace() will replace all occurrences, in case the substring occurs more than once. Based on your explanation, I assume this is what you want (if it's possible for a substring to occur more than once, to begin with).
If the substring is not found, String.Replace() will give you the same output as its input. Nothing will be changed. This means that you can execute your rule on your string without needing to check if the substring exists:
If it does exist, then your value will be replaced; just like you want it to happen.
If it does not exist, then nothing will happen; which is also what you want to happen.
You can dramatically simplify your code!
Create your dictionary;
Dictionary<string, string> rules = new Dictionary<string, string>();
rules.Add("abc", "aab");
rules.Add("ac", "ba");
rules.Add("cb", "cc");
Define your string:
string s = "aaaaaaabbbbbbccccccc";
And the rest is easy enough:
foreach(var rule in rules)
{
s = s.Replace(rule.Key, rule.Value);
}
This will try to perform a replace for every rule that you've defined. If it finds rules that are applicable; then it will replace the values.
Note
This code assumes that your replace values do not collide. If you do want to avoid collisions, you will have to check if substrings of all defined rules exist (Contains()) before actually replacing a value.
I have a really hard time understanding you requierment, but here is a solution may you tell me if this is even close to what you want?
private static string WeirdArrangement (string input)
{
//string input = "aabbcc[aczç_eyvur]";
string validChars = "abc";
string pattern = "abc"; // Must be a composition of all valid char
var invalidChars = input.Where(c => !validChars.Contains(c));
var validOccurences = input.Where(c => validChars.Contains(c))
.GroupBy(c => c)
.Select(c => new { Char = c.Key, Count = c.Count() });
var minPattern = validOccurences.Min(o => o.Count);
// Build time
StringBuilder builder = new StringBuilder();
//new StringBuilder(pattern.Length * minPattern + invalidChars.Count() + leftoverCount);
// X time partern
for (int i = 0; i < minPattern; i++) builder.Append(pattern);
//Rest of the validOccurences
foreach (var charOccurency in validOccurences)
{
for (int i = minPattern; i < charOccurency.Count; i++) builder.Append(charOccurency.Char);
}
//Invalid char
foreach (var invalidChar in invalidChars)
{
builder.Append(invalidChar);
};
return builder.ToString();
}
I'm trying to keep a parenthese within a string that's surrounded by a parenthese.
The string in question is: test (blue,(hmmm) derp)
The desired output into an array is: test and (blue,(hmmm) derp).
The current output is: (blue,, (hmm) and derp).
My current code is thatof this:
var input = Regex
.Split(line, #"(\([^()]*\))")
.Where(s => !string.IsNullOrEmpty(s))
.ToList();
How can i extract the text inside the outside parentheses (keeping them) and keep the inside parenthese as one string in an array?
EDIT:
To clarify my question, I want to ignore the inner parentheses and only split on the outer parentheses.
herpdediderp (orange,(hmm)) some other crap (red,hmm)
Should become:
herpdediderp, orange,(hmm), some other crap and red,hmm.
The code works for everything except the double parentheses: (orange,(hmm)) to orange,(hmm).
You can use the method
public string Trim(params char[] trimChars)
Like this
string trimmedLine = line.Trim('(', ')'); // Specify undesired leading and trailing chars.
// Specify separator characters for the split (here command and space):
string[] input = trimmedLine.Split(new[]{',', ' '}, StringSplitOptions.RemoveEmptyEntries);
If the line can start or end with 2 consecutive parentheses, use simply good old if-statements:
if (line.StartsWith("(")) {
line = line.Substring(1);
}
if (line.EndsWith(")")) {
line = line.Substring(0, line.Length - 1);
}
string[] input = line.Split(new[]{',', ' '},
Lot's o' guessing going on here - from me and the others. You could try
[^(]+|\([^(]*(?:\([^(]*\)[^(]*)*\)
It handles one level of parentheses recursion (could be extended though).
Here at regexstorm.
Visual illustration at regex101.
If this piques your interest, I'll add an explanation ;)
Edit:
If you need to use split, put the selection in to a group, like
([^(]+|\([^(]*(?:\([^(]*\)[^(]*)*\))
and filter out empty strings. See example here at ideone.
Edit 2:
Not quite sure what behaviour you want with multiple levels of parentheses, but I assume this could do it for you:
([^(]+|\([^(]*(?:\([^(]*(?:\([^(]*\)[^(]*)*\)[^(]*)*\))
^^^^^^^^^^^^^^^^^^^ added
For each level of recursion you want, you "just" add another inner level. So this is for two levels of recursion ;)
See it here at ideone.
Hopefully someone will come up with a regex. Here's my code answer.
static class ExtensionMethods
{
static public IEnumerable<string> GetStuffInsideParentheses(this IEnumerable<char> input)
{
int levels = 0;
var current = new Queue<char>();
foreach (char c in input)
{
if (levels == 0)
{
if (c == '(') levels++;
continue;
}
if (c == ')')
{
levels--;
if (levels == 0)
{
yield return new string(current.ToArray());
current.Clear();
continue;
}
}
if (c == '(')
{
levels++;
}
current.Enqueue(c);
}
}
}
Test program:
public class Program
{
public static void Main()
{
var input = new []
{
"(blue,(hmmm) derp)",
"herpdediderp (orange,(hmm)) some other crap (red,hmm)"
};
foreach ( var s in input )
{
var output = s.GetStuffInsideParentheses();
foreach ( var o in output )
{
Console.WriteLine(o);
}
Console.WriteLine();
}
}
}
Output:
blue,(hmmm) derp
orange,(hmm)
red,hmm
Code on DotNetFiddle
I think if you think about the problem backwards, it becomes a bit easier - don't split on what you don't what, extract what you do want.
The only slightly tricky part if matching nested parentheses, I assume you will only go one level deep.
The first example:
var s1 = "(blue, (hmmm) derp)";
var input = Regex.Matches(s1, #"\((?:\(.+?\)|[^()]+)+\)").Cast<Match>().Select(m => Regex.Matches(m.Value, #"\(\w+\)|\w+").Cast<Match>().Select(m2 => m2.Value).ToArray()).ToArray();
// input is string[][] { string[] { "blue", "(hmmm)", "derp" } }
The second example uses an extension method:
public static string TrimOutside(this string src, string openDelims, string closeDelims) {
if (!String.IsNullOrEmpty(src)) {
var openIndex = openDelims.IndexOf(src[0]);
if (openIndex >= 0 && src.EndsWith(closeDelims.Substring(openIndex, 1)))
src = src.Substring(1, src.Length - 2);
}
return src;
}
The code/patterns are different because the two examples are being handled differently:
var s2 = "herpdediderp (orange,(hmm)) some other crap (red,hmm)";
var input3 = Regex.Matches(s2, #"\w(?:\w| )+\w|\((?:[^(]+|\([^)]+\))+\)").Cast<Match>().Select(m => m.Value.TrimOutside("(",")")).ToArray();
// input2 is string[] { "herpdediderp", "orange,(hmm)", "some other crap", "red,hmm" }
I have variables containing text such as:
ShowSummary
ShowDetails
AccountDetails
Is there a simple way function / method in C# that I can apply to these variables to yield:
"Show Summary"
"Show Details"
"Account Details"
I was wondering about an extension method but I've never coded one and I am not sure where to start.
See this post by Jon Galloway and one by Phil
In the application I am currently working on, we have a delegate based split extension method. It looks like so:
public static string Split(this string target, Func<char, char, bool> shouldSplit, string splitFiller = " ")
{
if (target == null)
throw new ArgumentNullException("target");
if (shouldSplit == null)
throw new ArgumentNullException("shouldSplit");
if (String.IsNullOrEmpty(splitFiller))
throw new ArgumentNullException("splitFiller");
int targetLength = target.Length;
// We know the resulting string is going to be atleast the length of target
StringBuilder result = new StringBuilder(targetLength);
result.Append(target[0]);
// Loop from the second character to the last character.
for (int i = 1; i < targetLength; ++i)
{
char firstChar = target[i - 1];
char secondChar = target[i];
if (shouldSplit(firstChar, secondChar))
{
// If a split should be performed add in the filler
result.Append(splitFiller);
}
result.Append(secondChar);
}
return result.ToString();
}
Then it is could be used as follows:
string showSummary = "ShowSummary";
string spacedString = showSummary.Split((c1, c2) => Char.IsLower(c1) && Char.IsUpper(c2));
This allows you to split on any conditions between two chars, and insert a filler of your choice (default of a space).
The best would be to iterate through each character within the string. Check if the character is upper case. If so, insert a space character before it. Otherwise, move onto the next character.
Also, ideally start from the second character so that a space would not be inserted before the first character.
try something like this
var word = "AccountDetails";
word = string.Join(string.Empty,word
.Select(c => new string(c, 1)).Select(c => c[0] < 'Z' ? " " + c : c)).Trim();